The Relationship between Animal Welfare and Antimicrobial Use in Italian Dairy Farms

Information regarding the relationship between animal welfare (AW) and antimicrobial use (AMU) in dairy cows is limited. The current study aimed to investigate this relationship on Italian farms and to identify potential targets of AMU reduction. The study was performed at 79 Italian dairy farms housing over 15,000 cows during 2019. AW was scored with an on-farm protocol assessing farm management and staff training, housing systems, and animal-based measures. AMU was estimated using a defined daily dose per kg of animal biomass (DDDAit/biomass) for Italy. The median AW score was 73% (range: 56.6-86.8%). The median AMU was 4.8 DDDAit/biomass (range: 0-11.8). No relationship between the total AMU and AW was found. Management and staff training were positively associated with the use of the European Medicines Agency's category B antimicrobials, which are critical for human medicine, and with intramammary products for dry cow therapy. In those farms, antimicrobial stewardship should aim to reduce the category B antimicrobials and selective dry cow therapy. Our results underline the importance of implementing both an integrated monitoring system (AW, AMU, etc.) and antimicrobial stewardship tailored to the specific needs of each dairy farm.

Single unit activity of the suprachiasmatic nucleus and surrounding neurons during the wake-sleep cycle in mice

The suprachiasmatic nucleus (SCN) of the mammalian hypothalamus contains a circadian clock for timing of diverse neuronal, endocrine, and behavioral rhythms, such as the cycle of sleep and wakefulness. Using extracellular single unit recordings, we have determined, for the first time, the discharge activity of individual SCN neurons during the complete wake-sleep cycle in non-anesthetized, head restrained mice. SCN neurons (n=79) were divided into three types according to their regular (type I; n=38) or irregular (type II; n=19) discharge activity throughout the wake-sleep cycle or their quiescent activity during waking and irregular discharge activity during sleep (type III; n=22). The type I and II neurons displayed a long-duration action potential, while the type III neurons displayed either a short-duration or long-duration action potential. The type I neurons discharged exclusively as single isolated spikes, whereas the type II and III neurons fired as single isolated spikes, clusters, or bursts. The type I and II neurons showed wake-active, wake/paradoxical (or rapid eye movement) sleep-active, or state-unrelated activity profiles and were, respectively, mainly located in the ventral or dorsal region of the SCN. In contrast, the type III neurons displayed sleep-active discharge profiles and were mainly located in the lateral region of the SCN. The majority of type I and II neurons tested showed an increase in discharge rate following application of light to the animal's eyes. Of the 289 extra-SCN neurons recorded, those displaying sleep-active discharge profiles were mainly located dorsal to the SCN, whereas those displaying wake-active discharge profiles were mainly located lateral or dorsolateral to the SCN. This study shows heterogeneity of mouse SCN and surrounding anterior hypothalamic neurons and suggests differences in their topographic organization and roles in mammalian circadian rhythms and the regulation of sleep and wakefulness.

Mechanisms underlying obesity resistance associated with high spontaneous physical activity

Obesity resistance due to elevated orexin signaling is accompanied by high levels of spontaneous physical activity (SPA). The behavioral and neural mechanisms underlying this observation have not been fully worked out. We determined the contribution of hypothalamic orexin receptors (OXRs) to SPA stimulated by orexin A (OXA), whether OXA-stimulated SPA was secondary to arousal and whether voluntary wheel running led to compensations in 24-h SPA. We further tested whether orexin action on dopamine one receptors (DA1R) in the substantia nigra (SN) plays an important role in the generation of SPA. To test this, SPA response was determined in lean and obese rats with cannulae targeted toward the rostral lateral hypothalamus (rLH) or SN. Sleep/wake states were also measured in rats with rLH cannula and electroencephalogram/electromyogram radiotelemetry transmitters. SPA in lean rats was more sensitive to antagonism of the OX1R and in the early response to the orexin 2 agonist. OXA increased arousal equally in lean and obese rodents, which is discordant from the greater SPA response in lean rats. Obesity-resistant rats ran more and wheel running was directly related to 24-h SPA levels. The OX1R antagonist, SB-334867-A, and the DA1R antagonist, SCH3390, in SN more effectively reduced SPA stimulated by OXA in obesity-resistant rats. These data suggest OXA-stimulated SPA is not secondary to enhanced arousal, propensity for SPA parallels inclination to run and that orexin action on dopaminergic neurons in SN may participate in the mediation of SPA and running wheel activity.